.TH std::binary_function 3 "2024.06.10" "http://cppreference.com" "C++ Standard Libary"
.SH NAME
std::binary_function \- std::binary_function

.SH Synopsis
   Defined in header <functional>
   template<

       class Arg1,                 (deprecated in C++11)
       class Arg2,                 (removed in C++17)
       class Result

   > struct binary_function;

   std::binary_function is a base class for creating function objects with two
   arguments.

   std::binary_function does not define operator(); it is expected that derived classes
   will define this. std::binary_function provides only three types -
   first_argument_type, second_argument_type and result_type - defined by the template
   parameters.

   Some standard library function object adaptors, such as std::not2, require the
   function objects they adapt to have certain types defined; std::not2 requires the
   function object being adapted to have two types named first_argument_type and
   second_argument_type. Deriving function objects that take two arguments from
   std::binary_function is an easy way to make them compatible with those adaptors.

   std::binary_function is deprecated in C++11 and removed in C++17.

.SH Member types

   Type                 Definition
   first_argument_type  Arg1
   second_argument_type Arg2
   result_type          Result

.SH Example


// Run this code

 #include <algorithm>
 #include <functional>
 #include <iostream>
 #include <vector>

 struct same : std::binary_function<int, int, bool>
 {
     bool operator()(int a, int b) const { return a == b; }
 };

 int main()
 {
     std::vector<char> v1{'A', 'B', 'C', 'D', 'E'};
     std::vector<char> v2{'E', 'D', 'C', 'B', 'A'};
     std::vector<bool> v3(v1.size());

     std::transform(v1.begin(), v1.end(), v2.begin(), v3.begin(), std::not2(same()));

     std::cout << std::boolalpha;
     for (std::size_t i = 0; i < v1.size(); ++i)
         std::cout << v1[i] << " != " << v2[i] << " : " << v3[i] << '\\n';
 }

.SH Output:

 A != E : true
 B != D : true
 C != C : false
 D != B : true
 E != A : true

.SH See also

   function                   wraps callable object of any copy constructible type with
   \fI(C++11)\fP                    specified function call signature
                              \fI(class template)\fP
   move_only_function         wraps callable object of any type with specified function
   (C++23)                    call signature
                              \fI(class template)\fP
   ptr_fun                    creates an adaptor-compatible function object wrapper
   (deprecated in C++11)      from a pointer to function
   (removed in C++17)         \fI(function template)\fP
   pointer_to_binary_function adaptor-compatible wrapper for a pointer to binary
   (deprecated in C++11)      function
   (removed in C++17)         \fI(class template)\fP
   unary_function             adaptor-compatible unary function base class
   (deprecated in C++11)      \fI(class template)\fP
   (removed in C++17)
